diff --git a/src/main/java/rife/bld/extension/CheckstyleOperation.java b/src/main/java/rife/bld/extension/CheckstyleOperation.java
index d9b7b52..ed8a610 100644
--- a/src/main/java/rife/bld/extension/CheckstyleOperation.java
+++ b/src/main/java/rife/bld/extension/CheckstyleOperation.java
@@ -235,9 +235,9 @@ public class CheckstyleOperation extends AbstractProcessOperation<CheckstyleOper
             args.add(javaTool());
 
             args.add("-cp");
-            args.add(String.format("%s:%s:%s:%s", new File(project_.libTestDirectory(), "*"),
-                    new File(project_.libCompileDirectory(), "*"), project_.buildMainDirectory(),
-                    project_.buildTestDirectory()));
+            args.add(String.format("%s%s%s%s%s%s%s", new File(project_.libTestDirectory(), "*"),
+                    File.pathSeparator, new File(project_.libCompileDirectory(), "*"), File.pathSeparator,
+                    project_.buildMainDirectory(), File.pathSeparator, project_.buildTestDirectory()));
             args.add("com.puppycrawl.tools.checkstyle.Main");
 
             options_.forEach((k, v) -> {